Laser Radar Progress and Opportunities in Active Electro-Optical Sensing (2014) / Chapter Skim
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1 Introduction
1 Introduction
Pages 6-24
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From page 6... ...
For a synthetic aperture radar compared to a synthetic aperture ladar, this means flying 20,000 times shorter distance to form the synthetic aperture, but requiring motion compensation that is 20,000 times more accurate. Range resolution can also be higher than microwave radar because the high carrier frequency of active EO sensing allows very high bandwidth modulation to still be a small fractional bandwidth of the carrier.
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– This report uses "lidar" for active EO sensing of volume scattering targets. • Ladar (Laser Detection and Ranging)
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The laser illuminators in active EO sensing systems can raise eye safety issues for humans or animals in the beam path, as discussed in Box 1-4. Lasers operating in the wavelength region from about 400 nm to 1500 nm (blue to short wave infrared)
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waveforms. The same basic technology as used in the Raytheon implementation of the DARPA SALTI program; SALTI: Synthetic Aperture Lidar Tactical Imaging, a DARPA program to demonstrate synthetic aperture ladar from an airborne platform; RRDI: Range Resolved Doppler Imaging, a coherent ladar technique; PRN: Pseudo Random Number, a coded approach to correlation-based ranging; DIAL: Differential Absorption Lidar; PNR Photon Number Resolving (i.e., can measure 1, 2, 3, 4, ...
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BOX 1-3 The Laser Radar Range Equation The performance of an active EO system can be predicted by use of the laser radar range equation. The ladar equation calculates the laser power collected by the receiver.1 There are multiple forms of the ladar equation, depending on definitions and assumptions.
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government agency uses a software code that takes system inputs and evaluates eye exposure against the OSHA standards.2 Of course, observers in the beam path using binoculars or telescopes will experience a higher fluence than would the unaided eye, so eye safety for a person looking with binoculars would require a lower MPE. Figure 1-4-1 shows the MPE levels for laser pulses of various durations as a function of wavelength.
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5 The National Enhanced Elevation Assessment (NEEA) , sponsored by the United States Geological Survey (USGS)
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Since those early days, coherent ladar has blossomed to include ultraprecise range measurement, laser vibrometry, synthetic aperture ladar, spatial heterodyne imaging, ladar using multiple transmit and receive apertures, and to encompass a wide array of laser and detector technologies (see Chapter 3)
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Another very interesting feature of active EO sensing is the ability to gate out the light backscattered from obscurants. This results from the fact that it utilizes a high-bandwidth sensor with fine range resolution.
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"Wind sensing, navigation, long-range target tracking, terrain following, two-dimensional (2-D) and three dimensional (3-D)
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The committee expects that ladar will eventually replace most standard surveying techniques to provide native 3-D maps with significant economic benefits. Wind Sensing Global wind sensing can significantly improve weather prediction.
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Bevly, 2004, "The DARPA grand challenge: development of an autonomous vehicle," IEEE Intelligent Vehicles Symposium: 226. 19 Martin Buehler, Karl Iagnemma, and Sanjiv Singh, eds., 2007, The 2005 DARPA Grand Challenge: The Great Robot Race, Springer.
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Examples of domains include extraterrestrial rovers as well as possible future military applications such as battlefield robotics that may exploit other ladar technology features such as object identification for targeting or identify-friend-or-foe (IFF)
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can provide high-quality object identification for most objects with moving parts, such as engines. Synthetic aperture ladar can provide 2-D or possibly 3-D images at long ranges.
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In the future, oil companies may be able to explore for oil using laser vibrometers. Anytime there is a need to characterize object motion, a laser vibrometer will be a useful sensor.
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Also, coherent ladar can provide target velocity, and direct-detection ladars can use multiple range measurements to obtain velocity. Systems such as the Air Force Research Laboratory's (AFRL's)
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and tended to focus on the latter. Second, the committee focused on active EO technologies that might be developed by potential adversaries in the next 10-15 years to generate technological surprise.
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Conclusion 1-2: Active EO sensing offers many of the controlled illumination advantages of radar, and by operating at much shorter wavelengths enables greater range precision and angular resolution as well as more literal interpretability. Recommendation 1-1: To avoid the possibility of technological surprise, the U.S.
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24 LASER RADAR 700 600 500 400 China USA 300 W Europe 200 100 0 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 FIGURE 1-12 The number of publications on lidar or ladar per year is growing in the labeled countries/regions.
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